Abstract
This study examines the relationship between cerebral energy compounds and tissue oxygen availability. Ten ventilated lambs were studied under 40% N2O. Cerebral phosphorus-containing compounds (ATP, PCr, and Pi) were measured and intracellular pH (pHi) calculated using surface coil 31-P nuclear magnetic resonance (NMR) spectroscopy. The ratio of spectral peaks for PCr and Pi. (PCr/Pi) served as a. measure of bioenergetic reserve. Blood flow (Q) to the specific brain tissue detected by NMR was measured with microspheres (15 μ) and O2 delivery (OD) calculated (Q × O2 content). NMR spectra were taken continuously and flow measured after 7-9 minutes of hypoxia induced by decreased FIO2; arterial O2 content = 14.0 ± 0.8 (control), 7.0 ± 1.9, 2.2 ± 0.2, and 1.7 ± 0.03 vol % (mean ± SEM). Q was increased from control (114 ± 19) to 195 ± 36 and 282 ± 41 ml/min/100g at the two intermediate levels of hypoxia, but decreased during severe hypoxia (105 ± 59 ml/min/100g). PCr/Pi was 1.43 ± 0.03, 1.14 ± 0.10, 0.73 ± 0.08, and 0.54 ± 0.11, respectively. The relationship of PCr/Pi or pHi to O2 availability identifies a critical range of O2 availability (∼500 μmol/min/100g) below which cerebral bioenergetic reserve decreases linearly (PCr/Pi = OD × 0.00224 + 0.245, r = 0.65; pHi = OD × 0.00071 + 6.655, r = 0.57). The data underscore the importance of flow compensation and maintenance of oxygen delivery to preservation of cerebral energy metabolism during hypoxic stress in the newborn lamb. Inasmuch as the minimal requirement of O2 availability is 70% of control value (683 ± 91 μmol/min/100g), cerebral energy metabolism appears to be directly dependent on local blood flow alterations during hypoxemia.
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Wagerle, L., Delivoria-Papadopoulos, M., Younkin, D. et al. 1556 CEREBRAL BIOENERGETIC RESERVE AND BLOOD FLOW COMPENSATION IN HYPOXIC NEWBORN LAMBS. Pediatr Res 19, 370 (1985). https://doi.org/10.1203/00006450-198504000-01580
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DOI: https://doi.org/10.1203/00006450-198504000-01580